Morphing Mendel's Markers
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Linking genomics to plant breeding is akin to building a bridge connecting new DNA marker technology to traditional phenotypic trait analysis.
Morphologies have served as genetic markers since Mendel first connected single genes to single traits in peas. However, many important phenotypic traits are controlled by multiple genes.
This phenomenon comes into play breeding feedstocks for bioenergy, particularly selecting and optimizing candidate plant species or varieties for cellulosic conversion efficiency to ethanol coupled with maximum biomass production.
“Genes positively affecting cell-wall digestibility might undesirably affect biomass yield,” explains Thomas Lübberstedt, newly appointed director for the Raymond F. Baker Center for Plant Breeding, Kenneth J. Frey Endowed Chair and associate professor in the Department of Agronomy.
Lübberstedt is developing “functional markers” to help speed along bioenergy trait breeding efforts. Functional DNA markers tag regions of the genome that have been functionally characterized. They offer an advantage over random DNA markers because they are linked to functional pathways and can direct researchers where best to look for desired gene variants.
Working to optimize forage crops while at the Danish Institute of Agricultural Sciences, Lübberstedt began exploring the complex genetic interrelationships between stalk stamina and cell wall digestibility.
His work on maize (Zea mays L) a common forage crop in European agriculture, and the domestic ryegrass, Lolium perenne, “the major turf and forage grass in Europe and Australia and currently considered a valuable energy crop for marginal environments,” according to Lübberstedt, has thus far generated a handful of candidate functional markers from genes connected to cell wall digestibility.
Maize breeding efforts to date have created unprecedented grain yields. However, pest and stalk lodging resistance may come at a cost—digestibility, making the crop unsuitable for fermenter or fodder.
Maize Brown-midrib mutants used by Lübberstedt have desirable characteristics for cellulosic biofuel production, including decreased lignin content and an altered cell wall composition. But with these advantages comes susceptibility to lodging and lower biomass yield.
Understanding how these traits connect, “whether it is the same mechanism or just linkage,” says Lübberstedt will be important.
Growing up on a family horticultural farm outside Hamburg, Germany, did not inspire Lübberstedt to pursue farming as a profession. The family supplied vegetables and flowers to Hamburg and West Berlin which—prior to The Wall coming down—had no local agriculture of its own.
But while studying agronomy in Munich, “my interest was rekindled during my practical year spent on a farm studying maize,” he says.
However, small family farms in Germany were already becoming outmoded in favor of larger or more specialized farms, says Lübberstedt. So, he continued his studies, earning his doctorate in biology from the University of Munich, and launching a career in plant breeding.
“I'm an experimental person and enjoy developing the overall concept—then look for examples where these techniques make sense,” he says.
Other qualitites Lübberstedt is investigating include virus resistance in maize, forage quality, heterosis and vernalization—where some plants must experience a cycle of cold before flowering.
